Jaguar XJ8 Air Suspension Issues Explained(+3 Troubleshooting Tips)

In this brief article we are going to discuss the most common air Suspension issues that occur in the Jaguar XJ8,  what the causes are, and Troubleshooting Tips.

Top 3 Air Suspension problems in Jaguar XJ8

The Top 3 Air Suspension Issues in the XJ8 are:

  • ‘Air Suspension Fault’ diagnostic Error message
  • Tilted Stance
  • Hissing Noise when engine is running

What Suspension does the Jaguar XJ8 have?

The Jaguar XJ8 was part of the Jaguar XJ family of 4-door sedan luxury cars. The Jaguar XJ8  belongs to the X350 generation, produced from 2003 to 2009.

The XJ8 came with an Air suspension system as standard on all 4 corners. The front suspension is a Double Wishbone with Air Springs and Anti-Roll Bar.

The Rear Suspension on the XJ8 is a Double Wishbone with Air Springs and Anti-Roll Bar.

The XJ8 Air Suspension

  • The XJ8 air suspension is a passive system that provides vehicle ride height adjustment independent of load. 
  • At High speed, the system also improves the drag coefficient by automatically lowering the vehicle beyond a certain vehicle speed. When driving at high speeds, the air suspension system will lower the vehicle ride height to improve aerodynamics and vehicle stability. 
  • The suspension will automatically return to its normal ride height when the vehicle reduces speed.

NOTE:-

The XJ8’s Automatic-lowering beyond a preset Speed is disabled when towing since the towing payload already pushes the rear suspension down. Only Jaguar-approved towing equipment can turn Off Automatic Lowering.

Air Suspension Working Cycle

  • The air suspension system ensures that the vehicle is always at the proper ride height according to various load conditions.
  • The air suspension system automatically adjusts the air pressure in the air-bellows to level the vehicle. 
  • Air is supplied from the air reservoir or directly from the compressor. The compressor operates as and when it is required to maintain the required working pressure in the air reservoir.
  • The valve block opens and closes air supply to different parts of the system. The solenoids in the valve block are controlled by the Air Suspension Module (ASM)
  • The front air springs are controlled simultaneously, whereas the rear air springs are operated independently of each other. 
  • When lifting the vehicle the ASM controls the rear axle first; when lowering the vehicle the ASM controls the front axle first. The intention of this is to reduce headlamp glare to oncoming vehicles during ride height adjustments.

Suspension Height Sensors

The Suspension system has three suspension height sensors;  one mounted on the front subframe and 2 mounted on each side of the rear subframe. The suspension height sensors have mechanical links to the suspension arms via drop links. 

NOTE:-

If, for any reason, the Suspension height sensors are either refitted or replaced, they will require calibration each time this happens.

Air Springs/ Air Bellows

Two versions of the air spring are available, comfort and sport. The sport version works at slightly higher spring rate as compared to the comfort version. 

Each air springs version comes with its own version of dampers passive and active.

‘Air Suspension Fault’ diagnostic Error message

The Symptoms are:

  • Compressor overworking
  • Compressor unable to reach desired pressure within 2 minutes
  • The warning usually shows up after the 2 min delay within which the vehicle was supposed to have raised itself
  • Sometimes the message reads “Vehicle Too Low”
  • Lower-than-Normal Ride Height
  • Problem gets worse in Cold Weather

Root Cause for Air Suspension Fault Message

The fault happened because the Air compressor was not able to generate the required pressure within 2 min.

This could mean one of two possibilities:

  • There is a leakage within the system that is not allowing the air pressure to build up
  • The compressor is faulty or is worn out

Troubleshooting Air Suspension Fault Message: Air Leaks

  • Use soapy water or ‘Gas Leak Detector’ spray and check all the Air Springs and Air Connectors for Bubbles coming up
  • Pay particular attention to the Air Spring Top mount connectors
  • If leakage was detected at any of the connectors then either tighten the fitting or replace the O-ring between the two fittings.

Troubleshooting Air Suspension Fault Message: Air Compressor

  • In a majority of cases, the compressor still works, yet it is unable to develop pressure. The reason for this is end-of-life of the wear parts, namely, O-Rings and Piston Ring
  • There are DIY ‘Repair Kits’ available online
  • The Compressor is located right behind the Front Bumper on the LH side

Tilted Stance while parked

  • Either LH or RH side suspension sits higher with 1-2 inches of height difference when measured from the wheel center to the fender bottom

Root Cause for XJ8 Tilted Stance / Lean

  • If any suspension components like control arm, spring, etc. were replaced and then this error happens, because of a manual movement of the height sensor linkage of one particular corner during removal. On re-fitting, the sensor would have lost its calibration of vehicle height.

Troubleshooting XJ8 Tilted Stance

  • Try Resetting the Suspension
    • In the Boot under the spare wheel, you will find the Valve-box for the Air suspension system
    • Release all the air from the Rear LH & Rear RH (Blue and Red lines)
    • Make sure the ignition is OFF and the key is removed. Now, Remove the 20A fuse for the Air suspension from the Fuse box (also located within the Boot on the Right side)
    • After 15 mins put the Fuse back on and start the vehicle

Hissing Noise in XJ8 when engine is running

Root Cause

  • Once the engine starts, the compressor automatically comes on as well and tries to maintain the air pressure that is required for the suspension to function.
  • The Hissing noise is basically from a leakage point within the Air circuit. The fact that it is continuous, also gives us a clue that it is indeed from the air suspension system. The air suspension system tries to maintain pressure all the time. The leakage creates a drop in pressure, which the compressor tries to overcome by overworking.

Troubleshooting the XJ8 Hissing Noise

  • The leakage could be located anywhere in the system
  • But you can start with the weak points in the system, like Rubber Air Bellows (Air Springs) and connection joints, like the connections above the Air Spring
  • Also closely inspect the Air Springs themselves. Air bellows undergo massive wear and tear. Towards the end of the Air bellow’s service life, it develops cracks that would potentially turn into a leakage

Conclusion

In this brief article we have discussed the most common Air Suspension issues that occur in the Jaguar XJ8,  what the causes are, and Troubleshooting Tips.

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